BANGKOK (Reuters) - Thailand’s pig farmers are urging the government to resist pressure from the United States to open up its $3.5 billion pork market as U.S. President Donald Trump seeks to reduce U.S. trade deficits.

FILE PHOTO: A stall selling pork is seen at Maeklong market at the outskirts of Bangkok, Thailand September 21, 2016. REUTERS/Jorge Silva/File Photo

Dozens of farmers protested on Monday against any concessions as the Trump administration examines its trade deficit with Thailand, which reached nearly $19 billion last year.

Opening the pork market could affect major companies such as CP Foods Pcl (CPF.BK) and Thai Foods Group Pcl (TFG.BK) as well as an estimated 200,000 small producers.

“Prime Minister, I don’t eat American pork” read one of the banners addressed to junta leader Prayuth Chan-ocha. Political demonstrations are banned in Thailand, but the demonstration at the Commerce Ministry was allowed to take place peacefully.

One placard said: “No Poisoned Pork for Thai People, Keep your Stimulants” - referring to the use of the muscle-building drug ractopamine which is not banned in the United States and is the reason Thailand rejects U.S. pork imports.

Thailand raises about 18 million pigs a year with an estimated market value of $3.5 billion. Grilled, crispy, stewed, fried or made into sausages, pork is a prominent feature of Thailand’s world-renowned street food.

“We would like the commerce ministry’s support during negotiations,” the President of the Swine Raisers Association of Thailand Surachai Sutthitam told Reuters. Importing pork would ruin pig farmers and the suppliers of their feed, he said.

CP Foods and Thai Foods Group did not respond to requests for comment.

The U.S. Trade Representative has pressed Thailand to lift its ban on ractopamine and open the pork market to U.S. farmers.

Auramon Supthaweethum, the deputy head of Thailand’s Department of Trade Negotiations, told Reuters that a discussion of the import ban was “still being coordinated” with the Ministry of Agriculture and Cooperatives.

The Swine Raisers Association put the cost of raising pigs in Thailand at around $2 per kg. Lean hog futures 1LHV7 for October on the Chicago Mercantile Exchange are about $1.35 per kg.

Companies such as CP foods and Thai Foods not only buy pork from small producers, but also sell them feed.

Trump has invited Thai leader Prayuth to the White House, but no date has been announced.